Controlled oscillators, and in particular, analog controlled oscillators, have been in existence for many years. The general function of a controllable oscillator is to provide an output frequency which is related in some manner to a control input signal.
In an analog oscillator, the output frequency is generally controlled in accordance with an input voltage although at times it is controlled according to a current. In general, however, analog controllable oscillators have an output frequency which is a function of the gain of the oscillator and of the control voltage input.
In a digitally controlled oscillator such as presently described, the relationship between the output frequency and the control signal is quite different. The output frequency is generated by adding positive or negative increments of phase to the base reference frequency. The number of these increments added to the base reference rate per unit of time is a direct indication of the frequency output by the oscillator.
As is well-known, analog controlled oscillators are often affected by temperature and other environmental factors and in addition, often dissipate large amounts of power as heat. Since the present design is all digital, thus allowing it to be implemented in CMOS or other low power technologies, the generation of heat is minimized and the frequency control problems due to environmental conditions are non-existent.
It is thus an object of the present invention to provide an improved controlled oscillator apparatus.